Your Latest Issue of Cosmopolitan Includes a Survey of Readers

Your latest issue of Cosmopolitan includes a survey of readers on jealousy. You are asked to mail in your responses, and 19,000 responses are received. The results appear in the next issue. The results cannot validly be generalized to a population beyond the readership of Cosmo because

A) the sample size is inadequate
B) the sample is self-selected
C) the sample merely gathers testimonials
D) the survey is a correlation, not a causation